Health effects of oxidized fats and oils

1 Degree of oxidation/abuse. Studies with heated oils can be divided into two categories (a) oils that have been extensively oxidized/ abused and (b) oils that have been heated under conditions approximating normal cuUnary practices. Unlike the second type, the first type is usually prepared from experimental oils under unrealistic conditions. In this type, heated oil is not removed (with a fried product) and no new (make-up) oil is added. Since steady state conditions are not attained, such oils continuously deteriorate and the amount and types of oxidation products formed are directly related to heating time (Poling et al., 1960, 1962, 1970 Nolen, 1973). 

In addition to essential fatty acids and vitamin E, dietary protein levels have been shown to play an important role in the toxicity of oxidized fats/oils. Witting et al. (1957), for example, observed an almost total lack of growth in rats fed a diet containing laboratory prepared heated com oil and 10% casein. With 20% casein in the diet, severe growth depression was still seen, but at 30% or more protein in the diet, only a mild effect was observed. While the mechanism of the protective effects of high dietary protein is not yet clear, it may be linked to an enhanced detoxification capability. Long-term feeding of thermally oxidized fats, for example, has been shown to be associated with an induction of hepatic microsomal enzymes (Andia and Street, 1975). 

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